This glossary defines 46 terms you’ll meet on research-peptide product pages, batch reports and lab protocols, in plain English. Each definition stands on its own, so you can jump straight to the word you need.
Updated October 2026 · Pure Peptides Canada research team · Reference page
How the terms fit together
Most terms belong to one stage of a peptide’s path from synthesis to the bench: synthesize (SPPS, sequence, modifications), purify (RP-HPLC, counter-ion, TFA), freeze-dry (lyophilized, net peptide content), test (HPLC purity, MS identity, COA) and use in the lab (storage, molarity, dilution).
Testing and quality
| Term | Definition |
|---|---|
| Certificate of analysis (COA) | A laboratory report for one batch stating what was tested, how, by whom and the results. |
| HPLC | High-performance liquid chromatography: separates a sample’s components to measure purity. |
| Reverse-phase HPLC (RP-HPLC) | HPLC on a non-polar column, such as C18, that separates by hydrophobicity; the standard purity method for peptides. |
| Chromatogram | The HPLC trace of detector signal over time, with each component appearing as a peak. |
| Retention time | How long a component takes to leave the column; used to tell peaks apart. |
| Purity (HPLC) | The main peak’s share of the total peak area at the detection wavelength. |
| Mass spectrometry (MS) | Measures the mass-to-charge ratio of ions to confirm a molecule’s identity. |
| LC-MS | HPLC coupled to mass spectrometry, so each peak can be identified as it leaves the column. |
| ESI and MALDI | Two ways of ionizing peptides for MS: electrospray, which gives several charge states, and matrix-assisted laser desorption, which gives mostly single charges. |
| Theoretical mass | The mass calculated from a sequence and its modifications, compared with the observed mass. |
| Amino acid analysis (AAA) | Breaks a peptide into amino acids and quantifies them; used to determine net peptide content. |
| Karl Fischer titration | A test that measures residual water in a powder. |
| Endotoxin (LAL test) | Bacterial cell-wall material that can disrupt cell-based assays, measured with the Limulus amebocyte lysate test. |
| Verification key | A unique code that lets anyone confirm a report on the testing laboratory’s website. |
| ISO/IEC 17025 | The international standard for testing-laboratory competence; accreditation under it covers specific methods. |
For how these appear on a real report, see how to read a peptide COA and the HPLC testing guide. Endotoxin has its own explainer: endotoxin in research peptides.
Peptide chemistry
| Term | Definition |
|---|---|
| Amino acid | The building block of peptides and proteins; 20 are standard. |
| Peptide | A short chain of amino acids joined by peptide bonds; chains longer than about 50 amino acids are usually called proteins. |
| Peptide bond | The amide bond linking amino acids; it absorbs ultraviolet light near 214 nm. |
| Sequence | The order of amino acids, written from the N-terminus to the C-terminus in one- or three-letter codes. |
| N-terminus and C-terminus | The two ends of a peptide chain: the amine end and the carboxyl end. |
| Acetylation and amidation | Common end modifications, an acetyl group at the N-terminus or an amide at the C-terminus, which change mass and stability. |
| Solid-phase peptide synthesis (SPPS) | Builds a peptide one amino acid at a time on an insoluble resin. |
| Deletion sequence | An impurity missing one or more amino acids because a coupling step failed. |
| Oxidation and deamidation | Degradation reactions: oxidation of methionine, cysteine or tryptophan, and loss of an amide group from asparagine or glutamine. |
| Racemization | Conversion of an amino acid to its mirror-image form, creating closely related impurities. |
| Disulfide bond | A sulfur–sulfur link between two cysteine residues. |
Synthesis and its by-products are covered step by step in how research peptides are made; engineered modifications such as lipidation are in how peptides are made to last.
Form and composition
| Term | Definition |
|---|---|
| Lyophilized | Freeze-dried into a stable powder, often called a cake, by removing water under vacuum. |
| Counter-ion | The salt partner left from purification, such as trifluoroacetate, acetate or chloride. |
| Trifluoroacetate (TFA) | A common counter-ion from the acid used in purification; residual TFA can affect some cell-based assays. |
| Net peptide content | The share of a powder’s total weight that is peptide, after water and counter-ions. |
| Gross (fill) weight | The total powder weight in a vial, including water and salt. |
Why the last three differ, with a worked example: net peptide content and TFA vs acetate salts.
Solution math for in-vitro work
| Term | Definition |
|---|---|
| Molecular weight (MW) | The mass of one mole of a compound, in g/mol (numerically equal to daltons). |
| Molarity | Concentration in moles per litre (M); mM and µM are thousandths and millionths. |
| Stock solution | A concentrated solution that is diluted to make working solutions. |
| Aliquot | A measured portion divided from a larger volume, often frozen for single use. |
| C₁V₁ = C₂V₂ | The dilution equation linking stock concentration and volume to final concentration and volume. |
| Serial dilution | A series of stepwise dilutions, such as tenfold steps, used to reach low concentrations accurately. |
To work these out for a lab solution, use the peptide calculator for concentration, molarity and dilution.
Handling and logistics
| Term | Definition |
|---|---|
| Batch or lot number | A code identifying a production run; it links a vial to its report. |
| Cold chain | Temperature-controlled packaging and handling for products that need it. |
| Desiccant | A moisture-absorbing packet that keeps powder dry. |
| Freeze–thaw cycle | One round of freezing and thawing; repeated cycles degrade solutions. |
Practical handling is covered in the peptide storage guide and on the shipping across Canada page.
Regulatory terms in Canada
| Term | Definition |
|---|---|
| Research use only (RUO) | Supplied for laboratory research, not for human or veterinary use. Health Canada has said this labelling does not exempt a product from regulatory requirements. |
| In vitro and in vivo | “In glass” (test tubes, cell cultures) versus “in the living”, in an organism. |
| Drug Identification Number (DIN) | The eight-digit number on drugs authorized for sale in Canada. |
| Natural Product Number (NPN) | The eight-digit licence number on authorized natural health products. |
| Health Canada | The federal department that regulates drugs and health products in Canada. |
See the terms on a real product page
Our product pages put this vocabulary to work: vial size, lyophilized form, research-use status and where the test report can be found. These four are a good place to start.
BPC-15715-amino-acid research peptideView product
GHK-CuCopper tripeptideView product
TB-500Thymosin beta-4 research peptideView product
EpithalonLyophilized tetrapeptideView product
For laboratory research use only. Not for human or veterinary use.
Frequently asked questions
What does “lyophilized” mean?
Freeze-dried. Water is removed under vacuum from a frozen solution, leaving a dry, stable powder.
What is the difference between purity and net peptide content?
Purity compares the target peptide with related impurities; net peptide content compares all peptide with the vial’s total weight, including water and salt.
What is the difference between mM and µM?
1 mM equals 1,000 µM. Both are molar concentrations; millimolar is a thousand times more concentrated than micromolar.
Keep reading
- HPLC testing for research peptides: a plain-English guide
- Net peptide content and TFA vs acetate salts, explained
- How to spot fake or underdosed research peptides
- Research peptides in Canada: what they are and how to verify them
For laboratory research use only. Our products are not for human or veterinary use. This glossary is educational and is not medical or legal advice.
